| Cholesteric liquid crystals exhibit unique optical properties due to their periodic helical structure,and thus have promising applications in the field of optical materials.Among them,cholesteric liquid crystals with broadband reflectance properties have received extensive attention from researchers.Among the many methods for regulating the reflection band of cholesteric liquid crystal,electric field regulation has shown great potential for application due to its ease of operation,wide range of applications,practicality and stable adjustable bandwidth.It has been shown that the reflection bandwidth of polymer-stabilized cholesteric liquid crystals with negative dielectric anisotropy can be modulated by an applied DC electric field.The current research on the electric field-induced reflection band widening of polymer-stabilized cholesteric liquid crystals mainly focuses on how to widen the bandwidth and reduce the threshold voltage,etc.When the magnitude of the applied electric field is constant,the bandwidth and position of the reflection bandwidth cannot be regulated.In this paper,the effect of polymer network morphology on the DC electric field response of polymer stabilized cholesteric liquid crystals was investigated.The results show that the widening of the photonic band of polymer stabilized cholesteric liquid crystals is related to the concentration of polymerization monomers,and the DC electric field response of polymer stabilized cholesteric liquid crystals with lower monomer concentrations is more obvious,and the voltage required to widen the same band is smaller.When the monomer concentration is 6%-10%,the elastic modulus of the polymer network plays a major role in the electrical modulation of polymer stabilized cholesteric liquid crystals.A new polymer stabilized cholesteric liquid crystal with inhomogeneous polymer network distribution was successfully prepared by adding UV-absorbing dyes to the system to form a gradient distribution of light intensity within the liquid crystal cassette and using the difference in polymerization rate.The difference in polymer network density near the two substrates of the liquid crystals cell with the applied DC electric field was used to modulate the reflective bandwidth,which exhibited an obvious electrochromic difference.The factors influencing the spatial distribution inhomogeneity of polymer network were systematically investigated,and their effects on the gradient of polymer network distribution were explored by varying the liquid crystals cell thickness and dye concentration,and the gradient of polymer network distribution in polymer stabilized cholesteric phase liquid crystals was optimized,and the sensitivity of the electrically induced reflection bandwidth widening of polymer stabilized cholesteric liquid crystals to the direction of the applied DC electric field was demonstrated by relevant experiments.The polymer network distribution is not uniform.The research in this paper provides a new strategy for the regulation of the electrically induced reflective bandgap of polymer stabilized cholesteric liquid crystals,and broadens the ideas for the application of broadband reflective cholesteric liquid crystal materials with potential applications in optical data storage,smart windows,broadband polarizers,stealth technology,etc. |
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